JP2554806B2 - Floating height control method for strips - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the flying height of a belt-like body which ejects gas from a pad to convey the belt-like body.

[0002]

2. Description of the Related Art A non-contact supporting device at a position for changing the direction of a strip is known, for example, from Japanese Utility Model Publication No. 57-11971. In addition, in the steel strip connection annealing furnace, tension generators are installed on the inlet side and outlet side of the furnace, and a guide device is installed at the turning part to guide the non-contact transportation of the steel strip by the gas injection, and the steel strip is transported. Providing a turning portion that turns the direction has been proposed, for example, in Japanese Patent Laid-Open No. 2-61009.

[0003]

When carrying the belt-shaped body in a non-contact manner, it is desirable to save energy by setting the minimum gas flow rate. In particular, it is desired to prevent contact of the belt-shaped body at the turning portion of the belt-shaped body and stably support the belt-shaped body.
The present invention provides a method for automatically controlling the flying height of a belt-shaped non-contact supporting device.

[0004]

SUMMARY OF THE INVENTION The present invention controls the flying height by measuring the flying height and adjusting the flow rate of the floating fluid in accordance with the amount of change in the non-contact supporting and transporting of the strip. Is. Further, the flying height is estimated from the applied load and the conveying tension without measuring the flying height.

Further, when the plate width and the plate thickness are changed, the fluctuation of the flying height due to the abrupt change of the tension setting is predicted, and in consideration of it, the flow rate is adjusted in advance so that the flying height becomes appropriate. ◎ Flying height estimation model is learned during normal operation, and when the flying height detector or sensor control system fails, the sensor operation mode is automatically switched to the estimation model operation mode for control.

The present invention will be described in detail below. The present invention relates to a non-contact supporting device for a band (hereinafter referred to as a strip) including a pad (chamber) having one or a plurality of slits or ventilation holes, a blower for feeding a levitation fluid (hereinafter referred to as gas) to the pad, and a pipe. Then, the distance between the pad surface and the strip is measured, and the flow rate of gas fed to the pad is automatically adjusted so that the distance remains within a desired range.

In FIGS. 1, 2 and 3, the pad 10
Has a pressure chamber 2 and a guide surface 3, and the guide surface 3 is provided with slits 11-1 to 11-n. Reference numeral 12 represents an auxiliary nozzle. A flying height detector 13 is provided at a desired position on the guide surface 3. As the flying height detector 13, an eddy current type displacement gauge or a laser displacement gauge is used, but it is not particularly limited. In the present invention, the flying height adjuster 15 and the motor rotation speed controller 1
6, the motor 17 and the blower 18 are connected to the pipe 14-1.
˜14-n through slits 9-1 to -1 through valve 9
It is conducted to 1-n.

That is, in the flying height adjuster, the actually measured flying height is
The blower speed is controlled to match the set target value. The blower motor is preferably a variable speed type. Instead of controlling the rotation speed of the blower, a control valve may be provided on the inlet side or the outlet side of the blower to control the opening thereof.

In the present invention, the pad is divided into a plurality of zones in the transport direction, the flying height h of the strip from the pad surface is measured in each zone, and the flow rate of the floating gas in each zone is individually controlled. Extremely improved accuracy.

Another embodiment of the present invention will be described below. In this example, we measure the gas flow rate (and gas density) to the pad and the total loading of the strip on the pad surface and estimate the separation between the pad and the strip from them so that the estimate stays within the desired range. The flow rate of the gas sent to the pad is automatically adjusted.

In FIG. 4, the total load T and the orifice 1
Detection value the flying height of the pressure difference detector 30 of 9 estimation calculation unit 32
To enter. The flying height characteristic of the strip is expressed by equation (1). γu ² = (C · T · h ⁿ ) / L (1) where γ: specific weight of gas (kg / m ³ ) u: flow velocity from slit (m / sec) C: constant T: pad Total load (kg) h: Flying height (mm) n: Index (n = 1.3 to 2) L: Effective width between slits (m) C, n and L in the above formula depend on the pad. Determined. Further, γ is determined by the gas used, and T is determined by the operating conditions. Therefore, it can be seen from the above formula (1) that the flying height h can be controlled by adjusting the gas flow velocity u (gas flow rate into the pad).

That is, an orifice plate and its differential pressure detector are installed in order to measure the feed amount to the pad.
The differential pressure at the orifice is proportional to γu ² in equation (1). Therefore, if the total load T is input, the flying height h can be estimated from the equation (1).

The total load T is calculated by the following equation. T = 2t + G (2) However, t: Conveyance tension of the strip (kg) G: Weight of the strip applied to the pad (kg) Further, G is obtained as follows with reference to FIG.
When there are no welding points (strip joints) between rolls R ₁ and R ₂ . G = ρbws × 10 ⁻³ (3) where ρ: strip density (g / cm ³ ) b: strip thickness (mm) w: strip width (mm) s: strip length between rolls R ₁ and R _2. (M) When there is a welding point 31 between the strips 20-1 and 20-2 between the rolls R ₁ and R ₂ . G = {ρ ₁ b ₁ w ₁ (s−p) + ρ ₂ b ₂ w ₂ p} × 10 ⁻³ (4) where ρ: distance from roll R ₁ to welding point (m) Subscript 1: strip 1 Subscript 2: Strip 2 The distance p is automatically counted by tracking the welding point position.

Still another example of the present invention will be described. In this example, the decrease in the separation distance between the pad and the strip due to the sudden increase change in the total load applied to the pad that can be predicted is predicted in advance, and the separation distance is increased in advance in proportion to the predicted decrease. This prevents the separation distance from decreasing to an undesired degree even if a sudden increase in the total load occurs.

In FIG. 6, the total strip total load T
₁ and next strip total load T ₂ are input to calculate the flying height setting value.

The main disturbance in control is the fluctuation of the total load T in equation (2). However, the own weight G of T is a ramp-like change, and the flying height can be maintained substantially constant by the correction operation of the controller. However, in an annealing furnace or the like, the conveying tension t is generally changed within a few seconds depending on the size of the strip and the processing specifications when the joint of the strip reaches a predetermined place in the annealing furnace. With respect to this abrupt change, the correction operation of the adjuster alone cannot suffice and the flying height may be abnormally lowered.

To solve this problem, the flying height set value is increased in advance by an amount commensurate with the flying height that decreases due to the increase in tension, and the original height is set when the tension increases.

Now, the strip 20-1 is passing through the pad.
Let T _{1 be} the total load on the next strip 20-2, T ₂ be the total load on the next strip 20-2, and T ₂ > T ₁ . Even if the total load is suddenly changed from T ₁ to T ₂ , in order to maintain the target value h of the flying height, if the required flying height increment is Δh when the total load is T ₁ , then The relational expression of is established. T ₁ (h + Δh) ⁿ = T ₂ h ⁿ (5) That is, T ₂ / T ₁ = (1 + Δh / h) ⁿ (6) Here, in general, | Δh / h | <1 From equation (6), Δh is approximately expressed as follows. Δh = (T ₂ / T ₁ −1) h / n (7) However, T ₁ = 2t ₁ + G (8) T ₂ = 2t ₂ + G (9) t ₁ : Current strip 1 Actual transport tension (kg) t ₂ : Target transport tension (kg) of the next strip 2 The time course is shown in FIG. The actual total load on the pad is: Point _{P 1 ~P 3: T 1 P} 3 ~P 4: in the T ₁ T ₂ transition P ₄ to P _1: In T ₂ time P _2, (7) the calculated flying height setting a Δh by the formula Increase the height setting value of the vessel by Δh. As a result, by the flying height adjuster, after a certain period of time and before the time point P ₃ ,
The flying height becomes h + Δh. Indeed conveying tension at P ₃ is increased from t ₁ to t _2. That is, the total load increases from T ₁ to T ₂ in a short time. Time point P ₄ is when the increase of the conveyance tension is completed, and at this time, t ₁ = t ₂ ,
Since Δh in the equation (7) becomes 0, the flying height setting value returns to the original value h.

As a result, although it falls sharply from h + Δh to h between the time points P _{3 and} P ₄ , the original target value h can be maintained. Further, P ₃ is determined by the process, and P _{2 to} P ₃
The time of is determined by the response time of the control system.

FIG. 8 is a graph showing changes with time of the flying height h and the total load T according to this example. Δ commensurate with ΔT
By setting an appropriate flying height in anticipation of h, the rapid fluctuation of T can be absorbed, and stable operation can be continued.

Still another embodiment of the present invention will be described below.
In this example, the full load of the strip on the pad surface,
Also, the separation distance between the pad and the strip is measured, and the estimation accuracy is improved by learning the estimation model of the separation distance from them at all times.If the separation distance measuring device fails, the separation distance is automatically measured. To switch to the estimated value.

FIG. 9 shows the flow of this example. If the flying height detector is normal, use the detector signal. When there is an abnormality, the flying height detector failure signal automatically switches to the height estimation signal.

In order to estimate the flying height, it suffices to know C / L in the equation (1). However, in order to obtain the value with higher accuracy, it is better to actually measure the count. When actually measuring the counts, the measured values used include various noises. Therefore, when the flying height detector is normal, C
/ L is learned by the following equation, for example. (C / L) _{k + 1} = α {γu ² / Th ⁿ )} _{k + 1} + (1-α) (C / L) _k (10) However, K, K + 1; learning frequency α: coefficient ( 0 <α <1) The frequency of learning may be set, for example, every time the operating condition changes or the strip changes. If the flying height detector is abnormal, learning is stopped. When (C / L) is obtained in this way, this can be substituted into the equation (1) to estimate h from T and the orifice differential pressure signal γu ² .

Although the present invention has been mainly described with respect to the non-contact conveyance in the vertical strip turning section, the present invention can also be applied to the horizontal non-contact conveyance and the design can be changed within the scope of the object of the present invention. However, it does not depart from the scope of the present invention.

[0025]

According to the present invention, the flying height of the strip from the pad surface is measured and the flow rate of the floating fluid is controlled according to the amount of change, so that the strip can be accurately conveyed in a non-contact state. You can Furthermore, since the present invention calculates the total load of the strip and controls the flow rate of the levitation fluid according to the amount of change,
The strip can be conveyed in a non-contact state at the lowest gas flow rate.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a control method of the present invention.

FIG. 2 is a development view of a pad.

FIG. 3 is a partial cross-sectional view of a pad.

FIG. 4 is an explanatory diagram of another example of the present invention.

5 is a partial view of the control method of FIG.

FIG. 6 is an explanatory diagram of still another example of the present invention.

FIG. 7 is a chart for explaining the method of FIG. 6 over time.

8 is a graph of the method of FIG. 6 over time.

FIG. 9 is an explanatory diagram of still another example of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Hayashi 46-59 Nakahara, Tobata-ku, Kitakyushu City Nippon Steel Corporation Machinery & Plant Division (56) Reference JP-A-2-25219 (JP, A) JP-A-63-143227 (JP, A) Actually developed Shou 55-63338 (JP, U)

Claims (5)

(57) [Claims] 1. When feeding a fluid to a pad having a slit to convey the strip in a non-contact manner, the flying height h of the strip from the pad surface is measured, and the levitation fluid is determined according to the amount of change Δh. The flying height control method for a belt-shaped body, wherein the flying height h is controlled within a certain range by adjusting the flow rate of 2. The pad is divided into a plurality of zones in the transport direction, the flying height h of the strip from the pad surface is measured in each zone, and the flow rate of the levitation fluid in each zone is individually controlled. The flying height control method for a belt-shaped body according to claim 1. 3. When a fluid is fed to a pad having slits to convey a strip-shaped body in a non-contact manner, a total load T applied to the pad is calculated from the weight of the strip-shaped body applied to the pad and a tension for conveyance, and its change. By estimating the change amount Δh of the flying height of the strip from the pad surface according to the amount ΔT and adjusting the flow rate of the levitation fluid from the slit shown in equation (1), the flying height h A method for controlling the flying height of a strip, which is characterized by controlling the temperature within a certain range. γu ² = (C · T · h ⁿ ) / L (1) where γ: specific weight of fluid (kg / m ³ ) u: flow velocity from slit (m / sec) C: constant T: pad Total load (kg) h: flying height (mm) n: index (n = 1.3 to 2) L: effective width between slits (m) 4. A rapid variation ΔT of the total load applied to the pad is predicted, and a rapid variation Δh of the flying height of the strip from the pad surface due to the prediction Δh is estimated by the formula (2),
By controlling beforehand the fluctuation amount Δh of the flying height commensurate with the rapid fluctuation amount ΔT, it is possible to control the floating height of the strip within the control range when a sudden change in the total load occurs. The flying height control method for a strip-shaped body according to claim 3. Delta] h = {[(T ₂ / T ₁₎ -1] · h} / n ......... (2 ) provided that T _1: applied load of the current strip (kg) T _2: applied load follows strip (kg) h: Flying height (mm) n: Index (n = 1.3 to 2) 5. Delivery of fluid to a pad having slits
The non-contact conveyance of the belt-like body from the pad surface
If it is not possible to measure the flying height h of the strip,
It is applied to the pad due to the weight of the strip and the tension for transportation.
The total load T is calculated, and the pad is calculated according to the amount of change ΔT.
Estimate the change amount Δh of the flying height of the strip from the surface,
By adjusting the flow rate of the levitation fluid from the slit,
Therefore, the method for controlling the flying height h within a certain range is necessary.
Flying height control method of the belt according to claim 3, wherein the changing Ri.